The specific aims of this proposal are to (1) delineate the antigens responsibile for corneal graft rejection, (2) examine the immunological events leading to corneal rejection, and (3) attempt to manipulate those events to improve results of keratoplasty in high-risk cases. Three experimental systems will be used: An inbred rabbit model will examine in vitro activity of spleen, lymph node, and peripheral blood cells against donor corneal and lymphoid cells using proliferation, cell-mediated lysis, and leucocyte migration inhibition assays. Whole and absorbed rabbit serum will be evaluated against the same antigens by indirect immunofluorescence antibody-directed cytotoxicity and solid-phase radioimmunoassay techniques. The same model will evaluate the role of the T cell in rejection using a monoclonal reagent in vitro and Cyclosporin A in vivo. A guinea pig model (Strains 2 and 13) will evaluate in vitro the presence of laantigens on cornea by immunofluorescence and determine the role of la in rejection by a surgical model. A human model entirely in vitro will examine cellular and humoral aspects of corneal rejecton employing assays similar to the rabbit, monitor any change in the number of suppressor and helper T cells as a result of transplantation, and attempt to activate T cells which might suppress rejection. Based upon the results of the above study we hope to develop an in vitro assay which will identify prior to surgery those patients who for immunological reasons are at high risk of rejection. The results will also point the way for developing methods to alter the host immune response or the donor tissue in such a way as to improve results for tissue transplantation in general, and for keratoplasty in particular.